1. Field of the Invention
The instant disclosure relates to a control method for a power converter; in particular, to a control device for multiphase interleaved DC-DC converter and control method thereof.
2. Description of Related Art
European Standard IEC 61000-3-2 limits the distortion of the current harmonics of the input current caused by the electrical equipment. In order to reduce the distortion of the current harmonics and achieve higher power factor, a boost converter is most utilized. The boost converter with a single phase is usually utilized for the circuit having power consumption less than 300 watts. For the circuit having power consumption larger than 300 watts, the current ripple rises fast, such that a large EMI filter is needed accordingly. The boost converter usually operates in critical conduction mode (CRM) for obtaining higher power converting efficiency. The peak of the inductor current is twice as large as the average current, thus the switching loss is less and the conduction loss is larger. When the output power ranges from 400 watts to 800 watts which is refer to medium power applications, the peak of the inductor current of the single phase CRM PFC converter would be too large, so as to result larger power loss, and it is not conducive to the component selection accordingly.
In order to take advantage of the critical conduction mode in high power applications, the multiphase interleaved boost power factor correction circuit operating in critical conduction mode has been extensively studied to decrease the peak value of the input current ripple.
However, the variation of the operation frequency of the multiphase interleaved boost power factor correction circuit operating in critical conduction mode is quite large, thus the design of the control circuit is relatively complicated. Conventionally, the interleaved control could be divided to the open-loop control and the close-loop control. Referring to Huber, L., Irving, B. T., Jovanovi{grave over (c)}, M. M., “Open-Loop Control Method for Interleaved DCM/CCM Boundary Boost PFC Converters,” IEEE transactions on Power Electronics, vol. 23, no. 4, pp. 1649-1657, July 2008, the open-loop interleaved boost power factor correction circuit operating in critical conduction mode cannot return to a stable operating state when the turn-on signal is disturbed unless that the circuit operates in synchronized turn-on current mode (SNCM). On the other hand, the close-loop control needs a phase detector which usually is implemented by a phase-lock-loop (PLL) circuit for adjusting the phase difference. However, referring to Chung Ping Ku, Dan Chen, and Chin Yuan Liu, “A novel SFVM control scheme for two-phase interleaved CCM/DCM boundary mode boost converter in power factor correction applications,” in IEEE ECCE 2010, pp. 906-911, 12-16 Sep. 2010, the price of the phase-lock-loop circuit is expensive, the design of the phase-lock-loop circuit is more complex, meanwhile the phase-lock-loop circuit has bandwidth limitations.